This is a proposal to continue our investigations of patterns of eating behavior in lean and obese humans, both the microstructure of individual meals and meal and snack pattern over the 24-hours of the day. We are taking three steps in this work 1) A solid food unit (SFU) is being used as a laboratory food in order to monitor the rate and change in rate of eating over the time-course of a meal. Here we are investigating the effects of such major variables as deprivation, the time and size of preloads (to bias satiation), palatability, variety, and anorectic drugs on the microstructure of meals. Among other things, we are interested in learning why obese subjects don't slow down their eating as much as lean subjects as the meal progresses and what this implies about their responses to satiation cues. 2) The oral sensor is a piezo crystal, imbedded in a Hawley dental retainer that allows us to record all chews and swallows during a meal, and we are proposing to use it in the laboratory to record the time-course of eating complex, regular foods as well as SFUs. The same variables will be investigated, but now we can study the fine structure of eating by examining the rate of chewing, number of chews per swallow, and interswallow interval. We are expecially interested in following up the lead that the number of chews per swallow decreases as the palatability of the food increases and increases as the meal progresses and satiation develops. 3) Telemetering and ambulatory recording is being developed to broadcast the output of the piezo crystals to a 24-hour pocket tape recorder worn by the subject. This method will permit unobtrusive recording of all chews and swallows throughout the day so that all eating events can be recorded and we can analyze daily meal and snack patterns in lean and obese subjects in their natural environments outside the laboratory. We will measure meal size or duration, meal frequency, and intermeal interval (a) so that we can compare patterns in lean and obese people, (b) so that we can see the effects of perturbing the patterns by skipping or doubling and meal, and (c) so that we can measure the effects of anorectic drugs. It is our hope that this work will not only shed light on the fundamental process of human eating behavior, but will also distinguish eating patterns that lead to and maintain obesity. The fruits of these investigations may include the possibility of a behavioral classification of obesities, specific recommendations for behavioral modification of eating in weight-loss programs monitoring compliance to diet programs, and even the possibility of using the oral sensor system to signal patients when they eat too fast, too long, or too often.